1. Field of the Invention
This invention relates to a semiconductor device which includes a first semiconductor region of a first conductivity type formed in a semiconductor substrate, a second semiconductor region of a second conductivity type formed on the first semiconductor region in the semiconductor region, a third semiconductor region of the first conductivity type formed on the second semiconductor region, and electrodes arranged on the first, second and third semiconductor regions, respectively. More particularly, this invention is directed to a hetero-junction bipolar transistor or GCS (Gate Controlled Switch).
2. Description of the Prior Art
Generally, the energy band gap of an emitter region is wider than energy band gap of a base region or a collector region. The energy band gap functions as a barrier against minority carriers being injected from the base region. The rate at which minority carriers move toward the emitter region are recombined with electrons, is reduced by the barrier. Accordingly, base current I.sub.B is decreased, and a current gain will result. However, since the recombination speed is high in the junction, a transistor of sufficiently high current gain has not yet been developed.